Monash University terrorism expert Dr Peter Lentini told 7.30 people like Baryalei — those with troubled backgrounds — often saw conversion to Islam as a second chance.

"This type of a conversion gives them almost a second chance in life," he told the ABC.

On a mission .... Mohammad Ali Baryalei gained a devout following of young men.Source: Supplied

Baryalei, police allege, is behind an Islamic State plot to murder Australians on video.

NSW, Australian Federal Police and ASIO officers raided homes across Sydney and Brisbane last week after Baryalei allegedly spoke to Omarjan Azari by phone to discuss a plan to kidnap and murder – presumably by beheading – a random person on camera.

Baryalei — who was brought up in Sydney's northwest suburbs — was just a baby when his family fled Afghanistan.

Seven years later, they arrived at Sydney's Villawood detention centre.

The ABC says Baryalei's home life was troubled and he often clashed with his violet father.

After the September 11 attacks, something changed — he told friends he no longer felt welcome in Australia.

One friend told the ABC that Baryalei had suffered extreme bouts of depression and at one point spoke of suicide.

As a young man, he worked as a tout at John Ibrahim's Kings Cross brothel Love Machine.

Friends told 7.30 he embraced the fast-living, drug-fuelled lifestyle and liked to party hard.

Around this time, the ABC says, Baryalei had a religious epiphany and in 2012 he started going to a local mosque.

The one-time drug user became a born-again preacher and gained a devout following of young men in his mission to expose the failings of the Western world.

Secretly, he was recruiting his followers to take up arms in Syria and in April last year he travelled to the Middle East, the ABC says.

In April 2013 he reportedly travelled to the Turkey-Syria border, and soon joined up to Islamic State, where he has become the group's most senior Australian leader, allegedly responsible for recruiting foreign fighters.